The invention relates to a quick-change system for an excavator for the exchange of tools which are detachably fastened to an adapter of a bending arm by way of locking means and are held on the bending arm so that they can be swivelled around a horizonal axis.
From the German Patent Document DE-A 17 84 323, a quick-coupling system is known for connecting a tool with a bucket loader which comprises a pair of pins which can be engaged and disengaged with bores of the tool. The pins are operated by way of rods and reversing levers which are connected with a compressed-air cylinder. An arrangement of this type requires a relatively large amount of space, and the forces to be applied for adjusting the pins ar relatively high.
It is an object of the invention to provide a quick-change system which can be mounted in a space-saving manner on the bending arm as a structural unit, has a stable construction, and ensures a reliable connection between the tool and the bending arm.
According to the invention, this object is achieved by providing an arrangement wherein the locking means comprise piston means coaxially arranged in a housing and end-side locking pin means which, by way of an interposed pressure spring, can be adjusted into a moved-out operative position and, by way of a pressure admission controlled by a control unit, can be adjusted into a moved-in inoperative position inside the adapter.
The principal advantages achieved by the invention are that the locking pins are in a locking position as a result of an interposed single pressure spring, and the locking pins or the pistons of the locking pins are correspondingly acted upon by pressure only for the adjustment into an inoperative position (unlocked position). This ensures that the system in the locking position is solely subjected to the tension of the pressure spring and thus, when the pressure circuit fails, this position is nevertheless not endangered.
The locking elements, which consist of coaxially arranged pistons with locking pins in a cylindrical housing, are to be housed in an adapter in a space saving manner and can be dimensioned corresponding to the requirements with respect to the absorption of forces and moments. In particular, the hydraulic control circuit is designed such that a moving-back of the pistons can take place against the tension of the pressure spring. In order to promote the spring tension, according to another embodiment, the pistons can be acted upon by pressure also in the operating direction of the pressure spring.
According to the requirements of respective preferred embodiments, a structural unit may be used which consists of one pair of pistons with two locking pins or of two pairs of pistons with four locking pins.
The coaxial arrangement of the two pistons with the axial position of the pressure spring between the pistons results in a small compact structural unit which can be housed in the adapter in a simple manner and can easily be mounted and removed.
The adjustment of the pistons takes place by way of an operable multiple-way valve of the control unit which can be adjusted manually or electrically by means of a switch.
In the case of a construction of the quick-change system with only one locking element, the tool to be connected with the bending arm is hung in on the adapter. For this purpose, the adapter comprises a hook which, in a form-fitting manner, reaches around a cam of the tool.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.